1. Field of the Invention
The present invention relates to portable cutting devises, including those used for cutting trees or tree branches and those used for girdling a tree by cutting a strip of bark around the circumference of a tree. In addition, this invention is concerned with an apparatus for controlling a portable power cutting tool attached to the arm of the user and a method for using this apparatus.
2. Description of the Prior Art
It is common in the caretaking of forests to clear underbrush and extraneous trees from a forest to permit the optimum growth of the remaining trees. As well, in order for workers to move through a forested area underbrush, small trees and tree branches are often cleared to create or maintain a path through a forested area. It is also sometimes necessary to clear a forest of relatively mature trees. In the past forest workers have performed these operations with the use of small portable cutting devices which are usually designed to be hand held by the operator. Underbush clearing operations are commonly performed with the use of small handheld chainsaws. Clearing of mature trees is sometimes performed by a process known as "tree girdling". This process involves cutting a horizontal strip through the tree bark to the Cambian layer around the entire circumference of the tree. This process usually results in the death of the tree. An example of a hand held device used to girdle a tree may be found in U.S. Pat. No. 2,792,670 issued on May 21, 1957 to Haynes.
Hand held power cutting tools have proved to be unsatisfactory in cutting or girdling trees. Generally, both hands are required to control the power tool to ensure that the cut is properly placed on the tree and to ensure that the tool remains in the proper control of the operator. However, in moving through dense underbrush, it is desireable to leave one hand free to hold or push aside branches and small trees. It is also desireable to hold a part of the tree being cut or girdled, both to support the operator and to assist in the cutting process. Many hand held power tools cannot be operated properly with one hand. Those that might permit one handed operation are usually operated in an unsafe manner if operated by one hand. In addition, the operator's arm is generally subject to increased fatigue if a hand held power cutting tool is operated with only one hand.
A particular hazardous drawback of hand held cutting tools which utilize a rotating cutting edge (such as chainsaws) is the tendency for the cutting tool to "kickback" when jammed. The rotating part of the cutting tool, such as the chain of a chainsaw, when stopped or impaired, causes an upward force on the tool. This can be extremely dangerous to the user as the rotating chain or other cutting portion can be forced upwards and back to pivot towards the user and can seriously cut the user. The pivot point is generally the wrist of the hand of the user holding the cutting tool which is the weakest point between the user and the tool. The wrist is generally controlled by relatively weak muscle groups which are unable to properly control or prevent "kickback".
A further disadvantage of previous cutting tools is that separate cutting tools are necessary for girdling a tree and for cutting through a tree. Two separate tools are required to be carried by the user if he wishes to girdle some trees and cut through other trees or tree branches.